I am using the rounded corners plugin for jquery and have it working rounding elements in my page. The only issue I have is that the elements appear on the page un-rounded and then round. What do I need to do so that the elements only appear rounded?
I originally put my script tags in the head element but should they go somewhere else in a master page to improve perf?
this is because by default the elements are not rounded, it is the javascript that rounds them. It sounds like your js is taking a while to load and that's why you're seeing the flash.
to fix it you're going to have to get your .js loading faster. Typically this means reducing your page sizes. Also, while not recommended, you can move the javscript to the top of the page so it loads earlier and see if that has any effect.
Also there are different approaches to create rounded corner boxes using jQuery. What plugin do you use? My recommendation is http://jrc.meerbox.nl/?page_id=4 (Demo here)